Illumination apparatuses that use semiconductor light-emitting devices, such as LEDs, as a light source have been commercialized. In order to be mountable directly into existing lighting sockets for widespread incandescent bulbs, bulb-shaped LED lamps with a typical E26 base have been developed. In such a bulb-shaped LED lamp, a plurality of LED chips are generally mounted on a surface perpendicular to the central axis of the base. Light is emitted from each LED chip, which has strong directional characteristics, in the direction of the central axis of the base.
As a replacement for mini krypton bulbs, progress has also been made in the development of small bulb-shaped LED lamps with an E17 base, which is smaller than the typical E26 base. Mini krypton bulbs are often used in downlight fixtures. A small-bulb downlight fixture typically includes a socket and a hemispherical (bowl shaped) fixture body. The axis of the socket is approximately horizontal or is inclined at an angle of approximately 30° or less with respect to the horizon. The fixture body covers the mini krypton bulb whose base is mounted in the socket.
In the small-bulb downlight fixture, the hemispherical fixture body is attached to the ceiling or other surface so that an opening in the fixture body faces downwards. By being rotated through the opening of the fixture body, the base of the mini krypton bulb is mounted into the socket of the lighting fixture. Once mounted into the socket, the mini krypton bulb is maintained within the fixture body in an approximately horizontal position or inclined at an angle of approximately 30° or less with respect to the horizon.
In a conventional mini krypton bulb, since the spread angle of light is approximately 180°, centering on the light axis, light can be shone on a region below the lighting fixture when the bulb is mounted in the socket so that the axis of the socket is in a nearly horizontal state.
When a bulb-shaped LED lamp having a plurality of LED chips mounted on a surface perpendicular to the central axis of the base, as described above, is used as a replacement for a such a downlight mini krypton bulb, however, the light from the LED chips in the bulb-shaped LED lamp attached to the socket is emitted in a (forward) direction away from the base, along the central axis of the base. This leads to the risk of an insufficient amount of light being emitted towards the area of illumination below the lighting fixture.
Patent Literature 1 discloses a bulb-shaped LED lamp in which a cover housing a lighting device is attached to a base, and a spherical body provided with light-emitting diodes is attached so as to be rotatable with respect to the cover. In this bulb-shaped LED lamp, the direction of emission of light by the light-emitting diodes can be freely changed with respect to the axis of the base by rotating the spherical body with respect to the cover.
Furthermore, Patent Literature 2 discloses a bulb-shaped LED lamp in which a lighting circuit for lighting LEDs is provided inside a mount provided with a base, and LEDs are provided on the opposite side of the mount from the base with a rotating mechanism therebetween, the central light axis of the light beams emitted by the LEDs being at approximately a 90° angle with respect to the direction of insertion of the base.